Chambered flexographic ("flexo") ink units, employ two opposing, blades--a doctor blade and a sealer or containment blade--together with elastomeric end seals to form an enclosed chamber which contains ink being applied to a metering, ("anilox") roll. These two types of blades will hereafter be referred to collectively as "roll blades". A simplified yet typical flexographic printing system is depicted in FIG. 1 and is indicated generally at 10. A conventional, chambered flexographic ink unit or "inker" 12 adjoins and applies ink to a metering or anilox roll 14 of the system 10. The anilox roll 14 in turn applies its ink to the image carrier 16, typically a "flexo plate cylinder". Cylinder 16 in turn applies its ink to a flexible web 18 typically carried on a central drum 20 rolling against the flexo plate cylinder 16. Ink unit 12 is one of several such units which would be arrayed around the central drum.
As is further indicated in FIG. 2, the ink unit or "inker" 12 includes a body 30, which may be C-shaped in transverse cross section as indicated or of another shape. A recessed chamber 32 is formed into one side of the body facing the anilox roll 14 to receive ink to be printed on the web. A doctor blade 34 is typically clamped to the downstream edge of the holder body 30 by means of screws 38 and a clamping bar 40. A sealer or containment blade 36 is clamped to the upstream edge of the body 30 (see FIG. 1). There is typically one screw 38 every three to five inches of clamping bar 40 on ink units over twenty-two inches in length, (so-called "wide web" equipment) and one screw approximately every inch on ink units under twenty-two inches (so-called "narrow web" equipment). In this clamping configuration, the blades 34, 36 may be aligned to the holder body 30 by means of alignment pins 42 or, in some cases, machined "steps" (not depicted) in the holder body, which engage the back of the blades 34, 36 in a manner similar to the pins 42. Elastic seals 44 (e.g., "O-ring" strips) are provided between the blades 34, 36 and the body 30 to seal the blades with the body.
Doctor blades are typically installed nearly edge (i.e. nearly perpendicular to) on the anilox roll and are subject to significant pressure and wear. For that reason, they are made of steel, typically stainless steel or tool steel or steel otherwise treated to resist wear. Containment blades are generally installed at much shallower angles closer to tangent and are subject to significantly less pressure and wear than doctor blades. For that reason, containment blades are made from non-steel materials and can be made from non-metallic materials such as plastic.
A number of costs and operational problems exist with the existing means of clamping doctor and sealer or containment blades with screws. These are:
(A) Distortion of the clamp bar by non-uniform screw tightening. Uniform torquing of each screw with hand tools is difficult, time consuming and easily frustrated by varying degrees of individual screw-thread ink contamination, wear, damage and corrosion. This is a major cause of waviness, distortion or "ripples" in the clamped blade, resulting in doctoring and print defects and/or shortened blade life, as well as ink leakage paths under wavy, distorted or rippled doctor blades. PA1 (B) Increased costs and/or extended press make-ready time resulting from operators working to prevent or correct holder screw problems described in (A). PA1 (C) Difficult access to the inside of the "jaws" which hold the doctor and containment blades. Fast, easy and complete access to these surfaces is needed to remove dried ink which may be present, inspect jaw surfaces for scratches and other damage and/or replace blade ink seals if they are the type that require access, such as the O-ring strip seal 44 illustrated in FIG. 2. Removing ten or more holder screws to gain this access is very slow.